Dental caries is a major dental disease that affects the majority of the population. In the early part of the 20th century, investigators discovered that fluoride was effective in reducing the incidence of caries. Since that time, fluoride research has developed, and it is now well accepted that fluoride treatments benefit dental health.
Fluoride compositions are routinely applied to teeth by any number of methods and compositions, the most common methods by utilizing fluoride containing dentifrice compositions, such as toothpastes and mouthwashes. However, there are certain situations where it is desirable to have prolonged contact of the fluoride compositions with teeth, and to use amounts of fluoride that exceed fluoride amounts present in dentifrice compositions. For example, it may be desirable to treat xerostomia (dry mouth), tooth hypersensitivity, dental caries with high levels of fluoride for prolonged periods of time. This may be accomplished by the use of a dental tray, wherein a composition is applied to the dental tray, and then the composition and tray are applied to the teeth to be treated; however, this method is inconvenient, as the user is forced to retain the tray in their mouth during use, and thus the treatment time is limited by how long the user may retain the tray in their mouth. Thus, tooth varnish compositions have been developed to be applied directly to the tooth with a brush. The use of tooth varnish compositions are well known in the art, and the varnish compositions allow for a longer exposure time (e.g., about or greater than 2 hours) before the composition is worn away.
Existing tooth varnish compositions generally contain an active component, e.g., to treat caries, provide fluoride therapy, treat xerostomia, tooth sensitivity, and/or whiten or bleach teeth, and an adhesive film forming component to cause the active material to adhere to the tooth. However, due to the colour of the adhesive film forming component, the varnish may cause a temporary change in the surface colour of teeth, e.g., creating a yellow color. A color difference may be desirable in that it aids the user in identifying tooth surfaces on which the varnish has been applied; however, excessive color is undesirable, as yellow teeth suggest an unhygienic oral cavity, regardless of how temporary the varnish is. Additionally, the discoloration may cause embarrassment to the user, as others may realize that the user is utilizing a tooth varnish. Thus, there is a need to develop tooth varnish compositions which do not adversely affect the colour of a tooth.
Another disadvantage with tooth varnishes is that the varnishes tend to be multiphase, e.g., as the active component is insoluble in the adhesive film forming phase, and the varnish may separate out into distinct phases. Additionally, components of the adhesive film forming phase, may also separate into distinct phases over time. Users typically need to stir the varnish in order to mix the phases, which is time consuming and wasteful, as the varnish adheres to the mixing apparatus and is then discarded. Thus, there exists a need to develop tooth varnish compositions with greater stability, wherein the phases do not readily separate.